2 4 



NATURAL SCIENCE. 



July, 



possessing little or no diastase, there is always present more of this 

 ferment than is sufficient to transform all the starch they can ever 

 contain at one time, and in some cases the amount is such as would 

 transform a quantity of starch more than equal to the whole dry 

 weight of the leaf itself. 



The conflicting results previously obtained respecting this subject 

 are almost entirely due to the fact that although diastase is soluble 

 in water, it cannot readily be extracted from the leaf, on account of 

 the tenacity with which it is held by the protoplasm ; the presence 

 of considerable amounts of tannin also renders it insoluble. However, 

 by specially drying the leaf, and using the powdered tissue itself, it is 

 possible to demonstrate the presence of leaf diastase in all cases, and 

 these experiments give proof of its identity with the malt ferment ; 

 the production of the sugar maltose and dextrin from soluble starch 

 is brought about by both alike. 



The diastatic activity of the leaves of various species of plants 

 was compared, the results being very remarkable. The leaves of 

 leguminous plants stand far ahead of all others in this respect, the 

 garden pea heading the list. The relative diastatic activities are 

 stated in the amount in grams of maltose, which 10 grams of the air- 

 dried leaf will produce from soluble starch in 48 hours at 30 C. 

 Twenty-six species were examined, and the following are typical 

 results : — 



Pea (Pisum sativum) 



Scarlet Runner (Phaseolus multiflovus) 



Clover (Trifolium pratense) 



Vetch (Vicia sativa) 



Potato (Solatium tuberosum) 



Sunflower (Helianthus animus) 



Onion (Allium cepa) 



Cotyledon umbilicus 



Funkia sinensis 



Hymenophyllum demissum 



240 30 

 11049 

 8966 



79 55 



816 



394 

 376 

 4 61 



5'9i 

 420 



The work points to a connection between starch-forming power 

 and the diastatic power of leaves, but must be extended before any 

 general statement can be given. 



Changes in diastatic power of different portions of the same leaf 

 at different times of the day prove that the ferment increases as fast 

 as the leaf is being depleted of its starch and other assimilated pro- 

 ducts. Considerable accumulation takes place in the dark. They 

 believe that the secretion of diastase is only carried on by the proto- 

 plasm when the soluble nutriment of the cell has been used up or 

 carried out into the stem. At this starvation point diastase is 

 secreted in order to bring about the supply of soluble food-materia 

 from the reserve starch in the chloroplast. 



The last part of their memoir is concerned with the sugars of 

 the leaf, and this part of the work indirectly supports the unexpected 

 view that cane-sugar is the first sugar to be synthesised in the assimi- 



